This invention relates to improvements with respect to a brush seal used either as a primary or secondary seal for effecting a sealing relationships between a relatively rotatable shaft and a surrounding member such as a housing.
Brush seals have been utilized in various applications to effect a seal between relatively rotatable members. In most applications the sealing contact region between the brush seal and the member are relatively rotatable, and thus brush seals have been known to cause significant wear due to the abrasive effect of the metal brush bristles where they contact the rotating member. Recently there has been proposed a hybrid brush seal involving a floating rotor unit which mounts an annular brush thereon which in turn has a sealing engagement with a rotating shaft to create a primary or secondary seal therewith, which floating rotor unit is in its entirety rotatable with the shaft due to the frictional (i.e. interference) engagement between the free ends of the brush bristles and the shaft. This floating brush seal is typically used in combination with a face seal, preferably a noncontacting face seal, thereby defining primary and secondary seals which cooperate between the rotating shaft and the surrounding member. While a seal arrangement of this latter type is believed to possess desirable properties for many types of seal applications, nevertheless such seal arrangement is subject to ongoing development to improve the properties thereof.
This invention relates to a brush seal which employs a floating brush rotor which is disposed in concentric relationship with respect to a rotating member on which it is mounted and with which it creates a sealed relation, the latter sealed relationship also creating a support for the brush rotor so that it is substantially nonrotatably carried by the rotating member, the latter typically being a rotatable shaft. The floating brush rotor is, in the preferred embodiment, utilized as part of a hybrid seal which additionally incorporates a face-type seal so that the face and brush seals permit creation of primary and secondary sealing areas between relatively rotatable members.
In one improvement, the brush seal rotor includes a pair of annular brushes disposed in axially adjacent but spaced relation on a common rotor member so that the bristles of the two brushes sealingly engage a rotatable shaft, whereby an annular region is defined axially between the brushes and radially between the rotor and shaft. A supply passage projects through the rotor for communicating with the annular region to supply same with a buffer gas which is normally at a somewhat higher pressure than the process fluid pressure which exists adjacent one side of one of the brush seals. With this arrangement the buffer gas minimizes any migration of process fluid, particularly process liquid, through the brush seal while at the same time permits only minimal migration of buffer gas through the brush seal into the process fluid. The presence of buffer gas additionally helps maintain the bristle sealing areas free from build-up of debris.
Another improvement relates to a brush seal which is preferably floatably mounted relative to its sealing and supporting member and which additionally incorporates an annular gasket carried by the brush rotor in close proximity to the brush seal on the side thereof which faces the process fluid so that the gasket, due to its cooperation between the rotor and the support member or shaft, minimizes the exposure of the brush seal to the process fluid and thus greatly minimizes leakage of process fluid through the brush seal, particularly in those instances where the process fluid is a liquid.
A further improvement is a brush seal, particularly a floating brush seal which is used in combination with a double face seal, wherein the floating brush rotor is disposed between and defines thereon opposed sealing faces which cooperate with sealing faces defined on a pair of opposed stator seal rings mounted on the surrounding housing. The face seals are preferably gas seals so as to create a thin fluid sealing film between the opposed sealing faces. A spring energized seal is disposed for cooperation between one of the stator seal rings and the surrounding housing so as to urge this stator ring toward the rotor, thereby enabling the brush rotor and stator ring to relatively axially float to compensate for dimensional changes due to significant temperature variations, to allow the brush rotor to move axially relative to the shaft, and to provide pressure balancing across the seal assembly when the gas seals are used in conjunction with a pressurized buffer gas.
Structural and operational advantages of the seal arrangements disclosed herein will be apparent upon reading the following specification and inspecting the accompanying drawings.